A typical wind turbine generating apparatus is an apparatus which generates electricity by causing a rotor head with wind turbine blades to rotate upon receiving wind power, increasing the speed of rotation by a gear box, and thereby driving a generator. The rotor head is attached at an end portion of a nacelle that is installed on a tower erected on the ground or the like so as to be movable in a yaw direction. The rotor head is supported rotatably around a rotational axis in a substantially-horizontal lateral direction.
Heat generating devices including the generator are installed inside the nacelle. Heat generating devices such as a converter and a transformer are installed inside the tower. Thus, it is necessary to appropriately cool down the electric devices to keep stable operation. A wind turbine generating apparatus which introduces outside wind into a tower or a nacelle as cooling air has been proposed.
A pitch drive device is incorporated in the rotor head to adjust the pitch angle of the wind turbine blade to an optimum angle based on the air volume. Since the pitch drive device also generates heat during operation, the pitch drive device needs to be appropriately cooled down. For example, Patent Literature 1 discloses a wind turbine generating apparatus which employs a double-walled structure inside a rotor head, cools down a heat generating device installed inside an inner wall portion by introducing outside air from outside the rotor head into the inner wall portion, and discharges the air used for cooling to outside through the inside of a wind turbine blade.